Structural, optical, dielectric, and multiferroic properties of sodium and nickel co-substituted barium titanate ceramics

• Published in: Journal of materials science. Materials in electronics 2021-05, Vol.32 (10), p.12828-12840
• Main Authors: Alkathy, Mahmoud S., Eiras, J. A., Zabotto, Fabio. L., Raju, K. C. James
• Format: Article
• Language: English
• Subjects: Barium titanates; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Energy gap; Ferroelectric materials; Ferroelectricity; Grain size; Grain size distribution; Hysteresis loops; Magnetic properties; Materials Science; Nickel; Optical and Electronic Materials; Optical properties; Parameters; Perovskite structure; Perovskites; Room temperature; Sodium; Substitution reactions; Temperature dependence; Transition temperature; Vacancies
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-020-03900-y

Narrowing the bandgap energy of perovskite ferroelectrics is a potential task for improving PV applications. This study examined the effect of Ni 2+ /Na + co-substitution on the structural, optical, electrical, and magnetic properties of Ba 1- x (Ni x /2 ,Na x )TiO 3 (BTNaNi- x ) ceramics, where (0 ≤  x  ≤ 0.08), prepared by solid-state reaction method. X-ray diffraction along with structure refinement verifies the existence of perovskite structure with a tetragonal phase in all samples. The morphological study reveals a non-uniform grain size distribution with a decrease in grain size with an increase in co-substitution concentration. XPS study gives direct evidence of oxygen vacancies in the investigated sample. The oxygen vacancies and octahedral distortion accompanying the Ni 2+ /Na + co-substitution significantly reduce the optical bandgap of BaTiO 3 ceramics from 3.14 to 2.688 eV. The temperature dependence of the dielectric constant is measured in the range of 30–250 °C at the frequency of 1 kHz. The results reveal that the transition temperature gradually decreased with an increase in Ni 2+ and Na + concentrations. This phenomenon was interpreted based on reducing grain size and tetragonality with co-substitution. The ferroelectric and magnetic properties are determined by (P–E) and (M–H) hysteresis loops at room temperature . Magnetic properties are significantly enhanced with an increase in the Ni 2+ , Na + contents in the system. The correlation between the ESR width parameter (ΔH) and asymmetry parameter (Pays) with concentrations (x) reveals that the sample with x  = 0.08 has a strong magnetic nature compared to other samples.